title: A bifunctional invertebrate-type lysozyme from the disk abalone, Haliotis discus discus: genome organization, transcriptional profiling and biological activities of recombinant protein.
abstract: Lysozyme is an important enzyme in the innate immune system that plays a vital role in fighting microbial infections. In the current study, we identified, cloned, and characterized a gene that encodes an invertebrate-type lysozyme from the disk abalone, Haliotis discus discus (abLysI). The full-length cDNA of abLysI consisted of 545 bp with an open reading frame of 393 bp that encodes 131 amino acids. The theoretical molecular mass of mature abLysI was 12.3 kDa with an isoelectric point of 8.03. Conserved features in other homologs, such as catalytic sites for lytic activity (Glu(30) and Asp(41)), isopeptidase activity (His(107)), and ten cysteine residues were identified in abLysI. Genomic sequence analysis with respect to its cDNA showed that abLysI was organized into four exons interrupted by three introns. Several immune-related transcription factor binding sites were discovered in the putative promoter region. Homology and phylogeny analysis of abLysI depicted high identity and closer proximity, respectively, with an annelid i-type lysozyme from Hirudo medicinalis, and indicated that abLysI is a novel molluscan i-type lysozyme. Tissue-specific expressional studies revealed that abLysI is mainly transcribed in hepatopancreas followed by mantle. In addition, abLysI mRNA expression was induced following bacterial (Vibrio parahaemolyticus and Listeria monocytogenes) and viral (viral hemorrhagic septicemia virus) challenges. Recombinantly expressed abLysI [(r)abLysI] demonstrated strong lytic activity against Micrococcus lysodeikticus, isopeptidase activity, and antibacterial activity against several Gram-positive and Gram-negative bacteria. Moreover, (r)abLysI showed optimum lytic activity at pH 4.0 and 60 °C, while exhibiting optimum isopeptidase activity at pH 7.0. Taken together, these results indicate that abLysI is potentially involved in immune responses of the disk abalone to protect it from invaders.
authors.affiliation: Department of Marine Life Sciences, School of Marine Biomedical Sciences, Jeju National University, Jeju Self-Governing Province 690-756, Republic of Korea.
authors.forename: S D N K
authors.initials: SD
authors.lastname: Bathige
authors.forename: Navaneethaiyer
authors.initials: N
authors.lastname: Umasuthan
authors.forename: Saranya Revathy
authors.initials: SR
authors.lastname: Kasthuri
authors.forename: Ilson
authors.initials: I
authors.lastname: Whang
authors.forename: Bong-Soo
authors.initials: BS
authors.lastname: Lim
authors.forename: Bo-Hye
authors.initials: BH
authors.lastname: Nam
authors.forename: Jehee
authors.initials: J
authors.lastname: Lee
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D005091:Exons / Q000235:genetics; D049851:Gastropoda / Q000235:genetics* / Q000382:microbiology / Q000821:virology; D020869:Gene Expression Profiling; D015971:Gene Expression Regulation, Enzymologic; D054884:Host-Pathogen Interactions; D007438:Introns / Q000235:genetics; D007448:Invertebrates / Q000201:enzymology / Q000235:genetics; D008089:Listeria monocytogenes / Q000187:drug effects / Q000502:physiology; D008958:Models, Molecular; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009113:Muramidase / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D029141:Novirhabdovirus / Q000502:physiology; D016366:Open Reading Frames / Q000235:genetics; D010802:Phylogeny; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D014736:Vibrio parahaemolyticus / Q000187:drug effects / Q000502:physiology
chemical_list: D011994:Recombinant Proteins; D009113:Muramidase
keywords: Genomic structure; Haliotis discus discus; Immune response; Invertebrate-type lysozyme; Isopeptidase activity; Lytic activity